1. Field of the Invention
This invention relates to weapons and more particularly to a novel weapon selectively capable of firing only on targets having a particular radiative characteristic.
2. Description of the Background Art
In the past, it has been the conventional practice to employ a weapon having various aids to sighting the weapon: i.e., indicating to the operator the point of strike of the missile upon a visualized background or field of view. The effective use of such weapons has involved having the operator visually acquire a target image (whether by direct vision or by augmented vision such as image intensifier, video or thermal infrared telescope), aim the weapon by bringing the weapon sight (“crosshairs”) onto the target image, and choose the moment to manually pull a trigger to cause the weapon to discharge the missile.
The literature is rich in inventions to enhance respectively the sighting means, the manual trigger means, the ammunition, ammunition delivery mechanization, and the operator's optical/mechanical/electronic interface. It is very nearly empty of art addressing the problem of reliably firing the weapon on, and only on the target. Historically, the use of firearms to cause enemy casualties has been marginally effective. Some 5,000 rounds were fired in the American Civil War for each enemy casualty. Such ammunition expenditure rose in WWII to 35,000 rounds. American forces in Viet Nam are variously estimated to have expended 100,000 to 200,000 small-arms rounds, or some two to four tons of small-arms ammunition, per enemy casualty.
This problem of hitting the target is not primarily a challenge of firearm design. On a rifle range the soldier is trained for endless hours to compensate for mechanical and ballistic limitations of his weapon and to repeatedly put his bullets “in the black” of the small paper targets. The primary problem with firearm ineffectiveness in the field is the human involvement. This includes the time to notice and identify an uncertain and moving target, the time to bring the weapon into alignment, the erratic motion of the shooter at the best of times, his increased oscillation and shaking during combat, and the movement of the weapon as the trigger is jerked, and again as the firing pin plunges into the primer. When the target is running, hiding and shooting back, the soldier tends simply to fire as many bullets as he can as fast as he can in the general direction of the enemy, in hopes that some of them will hit something useful. Prior art firearms thus have the immediate safety disadvantage that almost no shot fired in combat causes an enemy casualty. Statistically, weapon fire in combat serves only to intimidate the enemy or to comfort the shooter. Further, bringing the ammunition to its point of use is a great logistics and soldier burden. In addition, the monetary cost of such combat expendables is large: of the order of the cost of a personnel vehicle.
What has been lacking in prior art is a weapon which can sense when a target is present at the projected point of impact of the missile, and precisely fire the weapon at that instant. This requires that a target sensor be provided with a firearm means which is capable of electric initiation, which discharges quickly in response to the electrical signal, and which provides repeating cycling without the delay and complexity of mechanical reloading. To be of practical value in combat, the sensor electronics must provide corrections for both target and weapon motion. The firearm must be free of mechanical vibrations or shaking which would disturb the quality of aim, and the entire system must be easily manufactured, low in cost, and rugged in field use.
A practical target sensor and method for integration with such a weapon has not been available. U.S. Pat. No. 5,392,688 (1995) shows the use of a television camera as a weapon sight for aiming, wherein the rifleman designates the “target” by placing the scope crosshairs on it and partially depressing the trigger. While it is not clear why the rifleman would at that point prefer simply to kill the target, this patent invokes an undisclosed “autolock-follow processor” circuit to differentiate and follow a target and ignore the background. Such capability is not generally known in the art. Further, the weapon is described simply as “fired electrically” and no useful firearm method is taught.
U.S. Pat. No. 4,370,914 (1983) teaches a gun-aiming method for calculationally averaging the swings of a rifleman's point of aim by gyroscopic measurement. The rifleman first designates the desired point of aim using his trigger switch. As said above, it is unclear why shooting at that point would not be preferable to later swinging back to that point and electrically firing the weapon. Of further disadvantage, the sighting method is taught by its claimed results, not as an limitable design or manufacture. Further, the use of a visible-light camera is taught and illustrated and claimed, which greatly limits the use of the method in combat. Further, no method for electrically firing the weapon is taught, but the electrical firing is simply invoked without teaching. Finally, no provision is taught for correcting for the effects of angular velocity either of the target or of the weapon; thus at best the taught method of aiming would be accurate only for a stationary weapon and stationary target.
Several methods in the art are intended to relate the weapon fire to the sensed presence of a target. U.S. Pat. No. 5,544,439 (1996) describes a modification to a prior art weapon with percussive firing, wherein the sear is operated by a solenoid in response to a target signal. The target signal is generated by a single infrared detector at the focal plane of a lens. In that only a single detector is used, the weapon can provide no compensation for either target motion or weapon motion. Additionally, no method of interpreting the signal to differentiate human radiation from other radiation patterns is taught. Use of electromechanical actuation has the disadvantages both of firing pin jolt and solenoidal mass acceleration. Both of these are likely to cause a significant movement of the point of aim between electronic “fire” command and the exit of the bullet from the barrel.
U.S. Pat. No. 5,966,859 (1999) describes the use of infrared radiation from a target imaged on a pyroelectric quad cell through unspecified optical filters, to cause a solenoid to pull the trigger on a gun. Pyroelectric detectors require the use of a mechanical chopper to modulate the incident optical beam on and off, with the inherent disadvantages of mechanical complexity, fragility and loss of half the target signal time. Further, use of a pyroelectric quad cell significantly limits the detection range due to its electronic noise. Additionally, no method is taught for interpreting the signal to differentiate human radiation from, e.g., flames. No provision is made for compensating the point of aim for target motion or weapon motion. The invention cannot deal with separate or overlapping targets, but would shoot exactly between two targets standing near each one another. The aiming disadvantages of mechanical percussion firing are further increased by the taught impulse motion and delay in action of a solenoid.
U.S. Pat. No. 6,174,288 (2001) couples the matter of U.S. Pat. No. 5,966,859 above with a heart-beat cycle aiming indicating device, with no abatement of the disadvantages noted above.
In the rich literature of inventions related to weapons, almost all firearms taught since 1900 describe or assume ammunition loads to be cartridges pre-packaged with ammunition and primer, loaded one at a time into the weapon receiver, and mechanically discharged by percussion on the primer. After firing, the chamber is cleared and a new ammunition load is introduced for firing. This procedure can be done in a single shot or manual manner or, as in automatic weapons, the pace or loading and unloading procedure cycled faster so that multiple rounds or shots can be fired in quick succession. However, it is to be understood that regardless of how fast the mechanism for loading and unloading may be driven by either recoil or external power, the sequence taught is first to load the firing chamber with the proper cartridge followed by firing of that cartridge and removal of the residue or cartridge casing which is then replaced by another cartridge or ammunition load preparatory to a second firing. Further, the method for igniting the propelling charge is typically mechanical: the fall of the firing pin on the primer. The use of percussion primers and associated physical components in modern firearms has imposed constraints which have inhibited significant advances in accuracy, safety, performance and reliability.
Although electronic components have been designed into the ignition systems of firearms, generally the electrical components either supplement or displace existing parts of the mechanical firing mechanism. A number of methods for discharging a weapon using an electrical signal have been taught in the art. These fall generally into one of two classes: electro-percussive firing of conventional primers, or electric ignition of flammable primers. Electro-percussive inventions are exemplified by the following.
U.S. Pat. No. 4,718,187 (1988) and U.S. Pat. No. 4,793,085 (1988) teach the use of a solenoid to actuate the firing pin, which increases the vibration problems of mechanical pulse.
U.S. Pat. No. 6,360,469 (2002) and U.S. Pat. No. 5,937,558 (1999) teach the use of a high voltage pulse through a mechanically driven firing pin to ignite the primer, which retains the vibration while adding a thermal pulse rise-time delay.
U.S. Pat. No. 4,285,153 (1981) describe a form of axially preloaded magazine in which the ammunition loads are sequentially fired through a plastic tube, inserted as a unit behind a separate smooth-bore weapon barrel. This disadvantageous separation of the ammunition from the barrel is overcome in U.S. Pat. No. 6,123,007 (2000) and U.S. Pat. No. 6,510,643 (2003), in which preloading of the actual barrel is taught. However, these last teach only a particular method of barrel assembly, and do not address the system issues of such an electrically actuated firearm, especially a means to direct the fire to the target.
Some electrical firearms using non-impact electric ignition of the primer have been developed, but with significant limitations. For examples, U.S. Pat. No. 4,332,098 (1982), U.S. Pat. No. 6,286,241 (2001) and U.S. Pat. No. 3,650,174 (1972) teach the use of a spring-loaded pin delivering a high voltage pulse to resistively heat and ignite the primer, which requires a relatively slow firing cycle. U.S. Pat. No. 5,625,972 (1997) discloses an electrically discharged firearm in which a heat sensitive primer is ignited by a voltage induced across a fuse wire extending through the primer. A laser ignited primer is disclosed in U.S. Pat. No. 5,272,828 (1993), wherein an optically transparent plug or window is centered in the case of the cartridge to permit laser ignition of the primer. In such a device, however, power requirements are substantial and limiting. In none of the devices of this paragraph is any other method of sustained fire feasible, except by mechanically rejecting spent cartridges and cycling another into the breech block, with the disadvantages of mechanical disturbance of the point of aim and slow cycle rate as already said.
Difficulties and problems have been encountered when employing such prior art devices and procedures which stem largely from the fact that the ammunition is loaded sequentially into the chamber which is time consuming and the firing is achieved through mechanical means which is slow in reaction time. Thus the prior art does not lend to nonmechanical rapid firing of ammunition loads nor lend to fast-response electronic control of the discharge. Additionally, the “fire” decision is not based on corrected prediction of the intersection of the point of impact on a human-spectrum radiator, including target motion and weapon motion.
In addition to the lack of a target sensor which is capable of sensing a target, differentiating it from the background, separating and locating intersecting target images, and compensating for weapon and target motion, and the lack of a fast-firing, non-mechanical, easily manufactured firearm component, provision of integration of such a target sensor with such a weapon has been lacking.
Therefore, a long standing need has existed to provide a novel weapon which fires only when the bullet or missile will usefully impact in a target. Further, a long standing need has existed to provide a target sensor combined with a corresponding novel weapon which weapon incorporates a plurality of ammunition loads which may be electronically detonated so as to fire individual or multiple loads from within the same firing chamber, and thus be amenable to near-instantaneous firing response to electrical signals from the target sensor, without mechanical impulse or vibration.